Field of the Invention
This invention relates generally to photodetectors, and more particularly to a detector architecture which enables co-located and near simultaneous operation in multiple modes.
Description of the Related Art
Conventional imaging systems that employ photodetectors are typically designed to operate in a pre-defined portion of the spectrum. For example, an imaging system might be designed to perform thermal imaging in the mid-wavelength infrared (MWIR) band. Another system could be arranged for imaging in the visible/short-wavelength IR (Vis/SWIR) portion of the spectrum, and yet another designed to provide low light level (LLL) night imaging.
All of the above functions have been demonstrated using individual imaging systems within the past few years. For example, single color MWIR n-on-p or p-on-n thermal imaging is a standard product throughout the IR industry. Several companies, such as Raytheon Vision Systems (RVS) and Selex, have demonstrated dual-band imagers which use an n/p/n architecture grown by MBE and MOCVD, respectively. Several companies, including RVS and BAE Systems, have generated so-called e-APDs using p-on-n material for LADAR and LLL applications.
In some applications, however, it would be highly preferred to have a single imaging system capable of providing data for all of the bands mentioned above. Heretofore, providing high performance across all of these bands requires the use of multiple focal plane arrays (FPAs), readout ICs (ROICs) and a complex optics train. However, this approach is costly and requires a large amount of area, and may be prone to reliability issues in view of the multiple independent systems needed.